Angular speed or angular velocity is a vector quantity which specifies the
axis that an object is rotating on. The SI unit of angular velocity is radians
per second, although it may be measured in other units such as degrees per second,
degrees per hour, etc. When measured in cycles or rotations per unit time, an
example of this is revolutions per minute.

James Watt who invented the term horsepower believes one horse can do 33,000
foot-pounds of work every minute. That means a horse generating 1 horse power
can raise 330 pounds 100 feet in one minute, 33 pounds 1,000 feet in one minute,
or 1,000 pounds 33 feet in one minute.

A truck engine has the same angular speed as a race car engine but only at
very low translational speed. From 40 mph and higher the truck engine has to
go to a second shift unlike the race car engine which is able to manage and
goes to its second shift at 80 mph. Even though a truck engine might not measure
greatly towards a race car's engine but truck engine's consistent speed help
carrying large and heavy loads for long distances and periods of time. Engine
performance is enhanced when the revolutions per minute are shortened. Trucks
use many different types of engines. They use gasoline engines, four stroke
turbo intercooler diesel engines, and locomotive-type engines such as a V12.